Why do we need measurements in physics

Current and voltage measurement

Current and voltage


We measure the current on an incandescent lamp. To do this, we connect it to a power supply unit.

What do we have to do if we want to increase the current in a lamp?

The electrical voltage is what drives the electrons. Therefore, the greater the electrical current in a circuit, the higher the voltage. The unit of voltage is the volt (from volta.
This is similar to water: the greater the water pressure on a pipe, the more water flows through it.


We measure the voltage at different voltage sources. To do this, we use batteries that we connect in series. This is also called series connection.

By connecting the batteries in series, we increase the electrical voltage.

How do you measure the voltage on a consumer in the circuit?

If we want to measure the voltage on a consumer, we have to connect the voltage measuring device in parallel to the consumer.

A small current flows through the measuring device. But in most cases this can be neglected.

The electrical voltage is a measure of the drive that electrons experience in a circuit. It is measured in volts. When measuring voltage, we do not need to open the circuit. We simply connect the voltage measuring device (voltmeter) in parallel to the consumer.
When batteries are connected in series, the voltages add up. The negative pole of one battery must always be connected to the positive pole of the following battery.

How does the current change when the voltage changes?

We measure current and voltage simultaneously on an incandescent lamp. We want to investigate how the current changes when the voltage is changed.

Measuring circuit

We connect the current measuring device (ammeter) in series to the consumer. On the other hand, we connect the voltage measuring device (voltmeter) in parallel to the consumer.

A small current flows through the voltmeter, otherwise we would not have a rash. However, this current is much less than the current that flows through the incandescent lamp.

The measurement result on the ammeter is slightly falsified.

Measurement on a resistor

What does electrical resistance mean?

If current flows through a metallic conductor, the free electrons move between the atoms of the conductor material. The atoms swing in all directions around their position of rest. This hampers the movement of the free electrons. Each conductor therefore opposes the electrical current with a resistance which the voltage has to overcome.

Here you will find a Overview of further articles on the subject of measurements in electric circuits, electromagnets,it also contains links to tasks.

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